Derive for deomcracy nextExternal (#2108)

packages/api-derive/src/democracy/index.ts

@@ -6,6 +6,8 @@ export * from './_referendumsVotes';
 export * from './_referendumVotes';
 export * from './_referendumInfo';
 export * from './dispatchQueue';
+export * from './nextExternal';
+export * from './preimage';
 export * from './preimages';
 export * from './proposals';
 export * from './referendums';

packages/api-derive/src/democracy/nextExternal.ts

@@ -0,0 +1,40 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { Hash, VoteThreshold } from '@polkadot/types/interfaces';
+import { ITuple } from '@polkadot/types/types';
+import { DeriveProposalExternal } from '../types';
+
+import { Observable, of } from 'rxjs';
+import { map, switchMap } from 'rxjs/operators';
+import { ApiInterfaceRx } from '@polkadot/api/types';
+import { Option } from '@polkadot/types';
+
+import { memo } from '../util';
+
+function withImage (api: ApiInterfaceRx, nextOpt: Option<ITuple<[Hash, VoteThreshold]>>): Observable<DeriveProposalExternal | null> {
+  if (nextOpt.isNone) {
+    return of(null);
+  }
+
+  const [imageHash, threshold] = nextOpt.unwrap();
+
+  return api.derive.democracy.preimage(imageHash).pipe(
+    map((image): DeriveProposalExternal => ({
+      image,
+      imageHash,
+      threshold
+    }))
+  );
+}
+
+export function nextExternal (api: ApiInterfaceRx): () => Observable<DeriveProposalExternal | null> {
+  return memo((): Observable<DeriveProposalExternal | null> =>
+    api.query.democracy?.nextExternal
+      ? api.query.democracy.nextExternal<Option<ITuple<[Hash, VoteThreshold]>>>().pipe(
+        switchMap((nextOpt) => withImage(api, nextOpt))
+      )
+      : of(null)
+  );
+}

packages/api-derive/src/democracy/preimage.ts

@@ -0,0 +1,25 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { AccountId, Balance, BlockNumber, Hash } from '@polkadot/types/interfaces';
+import { ITuple } from '@polkadot/types/types';
+import { ApiInterfaceRx } from '@polkadot/api/types';
+import { DeriveProposalImage } from '../types';
+
+import { Observable } from 'rxjs';
+import { map } from 'rxjs/operators';
+import { Bytes, Option } from '@polkadot/types';
+
+import { memo } from '../util';
+import { parseImage } from './util';
+
+type PreImage = Option<ITuple<[Bytes, AccountId, Balance, BlockNumber]>>;
+
+export function preimage (api: ApiInterfaceRx): (hash: Hash) => Observable<DeriveProposalImage | undefined> {
+  return memo((hashes: Hash[]): Observable<DeriveProposalImage | undefined> =>
+    api.query.democracy.preimages<PreImage>(hashes).pipe(
+      map((imageOpt) => parseImage(api, imageOpt))
+    )
+  );
+}

packages/api-derive/src/democracy/types.ts

@@ -2,7 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { AccountId, Balance, BlockNumber, Hash, Proposal, PropIndex, ReferendumInfoTo239, ReferendumStatus, Vote, ReferendumIndex } from '@polkadot/types/interfaces';
+import { AccountId, Balance, BlockNumber, Hash, Proposal, PropIndex, ReferendumInfoTo239, ReferendumStatus, Vote, ReferendumIndex, VoteThreshold } from '@polkadot/types/interfaces';
 
 import BN from 'bn.js';
 import { Vec } from '@polkadot/types';
@@ -30,6 +30,12 @@ export interface DeriveProposal {
   seconds: Vec<AccountId>;
 }
 
+export interface DeriveProposalExternal {
+  image?: DeriveProposalImage;
+  imageHash: Hash;
+  threshold: VoteThreshold;
+}
+
 export interface DeriveReferendum {
   index: ReferendumIndex;
   image?: DeriveProposalImage;